FIBERSIM(R)在无人机复合材料部件开发中的优点

FiberSIM能辅助无人机复合材料结构在更低的成本下取得更轻的重量,同时能标准化和自动化完成开发过程。高空无人机的机身约占起飞总重的三分之一。任何对机身的减重都直接转化成增加传感器或有效载荷、飞行持续时间。因此制造者专注于采用工业定义的工程过程来设计     

在温莎,有着被世界公认的最著名的学校——伊顿公学

英国温莎和上海完全是天壤之别的。温莎是一个传统的英式小镇,坐落在泰晤士河畔,离伦敦东部20英里,小卵石铺就的街道两旁坐落着小商店和餐馆,而上海是一个生机勃勃的现代化大都市,到处都是马路,商店和人。那么是什么使温莎变得特别呢?首先她是英国女王的主要住所温莎城堡的所在地,而且她有着被世界公认的最著名的学校——伊顿公学。     

The possible origin and persistence of life on Enceladus and detection of biomarkers in the plume

The jets of icy particles and water vapor issuing from the south pole of Enceladus are evidence for activity driven by some geophysical energy source. The vapor has also been shown to contain simple organic compounds, and the south polar terrain is bathed in excess heat coming from below. The source of the ice and vapor, and the mechanisms that accelerate the material into space, remain obscure. However, it is possible that a liquid water environment exists beneath the south polar cap, which may be conducive to life. Several theories for the origin of life on Earth would apply to Enceladus. These are (1) origin in an organic-rich mixture, (2) origin in the redox gradient of a submarine vent, and (3) panspermia. There are three microbial ecosystems on Earth that do not rely on sunlight, oxygen, or organics produced at the surface and, thus, provide analogues for possible ecologies on Enceladus. Two of these ecosystems are found deep in volcanic rock, and the primary productivity is based on the consumption by methanogens of hydrogen produced by rock reactions with water. The third ecosystem is found deep below the surface in South Africa and is based on sulfur-reducing bacteria consuming hydrogen and sulfate, both of which are ultimately produced by radioactive decay. Methane has been detected in the plume of Enceladus and may be biological in origin. An indicator of biological origin may be the ratio of non-methane hydrocarbons to methane, which is very low (0.001) for biological sources but is higher (0.1-0.01) for nonbiological sources. Thus, Cassini's instruments may detect plausible evidence for life by analysis of hydrocarbons in the plume during close encounters.     

一种多级火箭飞行方案设计的工程方法

提出了一种进行单级和多级火箭飞行方案设计的一般方法。这是一种基于微积分变分原理的工程方法。其目的是根据给定导弹的攻角方案设计其俯仰角方案。最大攻角的优化根据给定的初始设计值采用正交法进行。该方法可以快速地进行多级火箭的飞行方案设计。     

Serpentinization and its implications for life on the early Earth and Mars

Ophiolites, sections of ocean crust tectonically displaced onto land, offer significant potential to support chemolithoautotrophic life through the provision of energy and reducing power during aqueous alteration of their highly reduced mineralogies. There is substantial chemical disequilibrium between the primary olivine and pyroxene mineralogy of these ophiolites and the fluids circulating through them. This disequilibrium represents a potential source of chemical energy that could sustain life. Moreover, E (h)-pH conditions resulting from rock- water interactions in ultrabasic rocks are conducive to important abiotic processes antecedent to the origin of life. Serpentinization--the reaction of olivine- and pyroxene-rich rocks with water--produces magnetite, hydroxide, and serpentine minerals, and liberates molecular hydrogen, a source of energy and electrons that can be readily utilized by a broad array of chemosynthetic organisms. These systems are viewed as important analogs for potential early ecosystems on both Earth and Mars, where highly reducing mineralogy was likely widespread in an undifferentiated crust. Secondary phases precipitated during serpentinization have the capability to preserve organic or mineral biosignatures. We describe the petrology and mineral chemistry of an ophiolite-hosted cold spring in northern California and propose criteria to aid in the identification of serpentinizing terranes on Mars that have the potential to harbor chemosynthetic life.     

Detectability of planetary characteristics in disk-averaged spectra II: synthetic spectra and light-curves of earth

Spatially and spectrally resolved models were used to explore the observational sensitivity to changes in atmospheric and surface properties and the detectability of surface biosignatures in the globally averaged spectra and light-curves of the Earth. Compared with previous efforts to characterize the Earth using disk-averaged models, a more comprehensive and realistic treatment of the surface and atmosphere was taken into account here. Our results are presented as a function of viewing geometry and phases at both visible/near-infrared (0.5-1.7 microm) and mid-infrared (5-25 microm) wavelength ranges, applicable to the proposed NASA-Terrestrial Planet Finder visible coronagraph and mid-infrared interferometer and to the ESADarwin mission architectures. Clouds can change the thermal emission by as much as 50% compared with the cloud-free case and increase the visible albedo by up to 500% for completely overcast cases at the dichotomy phase. Depending on the observed phase and their distribution and type, clouds can also significantly alter the spectral shape. Moreover, clouds impact the detectability of surface biosignatures in the visible wavelength range. Modeling the disk-averaged sensitivity to the "red-edge," a distinctive spectral signature of vegetation, showed that Earth's land vegetation could be seen in disk-averaged spectra, even with cloud cover, when the signal was averaged over the daily time scale. We found that vegetation is more readily discriminated from clouds at dichotomy (50% illumination) rather than at full phase. The detectability of phytoplankton was also explored, but was found to be more difficult to detect in the disk-average than land vegetation.     

企业信息化术语

1 DSS（Decision Support System,决策支持系统）——是围绕着决策行动主体进行的支持管理人员进行非程序性决策的一种信息系统。决策支持系统具有如下三个特征：（1）以处理非程序性决策为主；（2）是对管理人员决策的支持而不是代替；（3）系统本身要求具有灵活性，采用联机对话方式，以便利用人的经验和系统提供可供分析的信息来解决问题。目前的DSS一般由一个数据库、一个模型库以及复杂的软件系统构成。2 ESS（Executive Support System,高层主管支持系统）——是综合了各种信息报告系统和决策支持系统的特色而构成的一种专为组…     

2001年航天工艺信息网征文通知

根据2001年3月9日航天工艺信息网网长、在京副网长、联络员工作会议精神，拟定于2001年下半年召开2001年航天工艺学术交流会(具体时间、地点另行通知)。交流会将以崭新的面貌供航天科技人员交流经验、切磋技艺，无疑会对促进和提高航天工艺技术、活跃学术气氛起到积极作用。希望各网员单位和广大科技人员积极投稿，踊跃参加。有关事项通知如下。一、征文内容1．综述航天工艺技术的成就、问题、前景等。2．航天新工艺、新技术、新材料的国外应用情况及其展望。3．精密铸造、焊接、热处理、化铣、超塑成型等特种工艺技术的应用与发展。4．复合…     

合成孔径雷达图像中目标的统计特性

本文讨论了合成孔径雷达（SAR）图像中目标的统计特性，并验证了如何利用这一特性进行自动SAR目标分类及识别。文中介绍了一种用于估计目标雷达横截面积的目标平滑算法，这种算法可以与适当的噪声模式相结合以针对给定的成像构造产生多个目标，这就允许对目标特性进行统计分析，用于改进基于特征的分类，并通过对真实目标进行简单的分类实验进行了验证。